Apparatus for making preformed seals

ABSTRACT

A method of making a preformed seal includes coupling first and second sections of a mold to define a mold cavity. A cross-sectional shape of the mold cavity corresponds to a cross-sectional shape of the preformed seal. The method also includes providing a reservoir that has a port in flow communication with a reservoir cavity that extends to a parting surface. The method further includes filling the reservoir cavity with wet sealant such that the wet sealant is flush with the parting surface and a bead of wet sealant protrudes from the port. Additionally, the method includes coupling the reservoir to the first and second sections such that the reservoir cavity is in flow communication with the mold cavity at the parting surface, injecting wet sealant from a nozzle through the reservoir into the mold cavity, and curing the wet sealant in the mold cavity to make the preformed seal.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional and claims priority to U.S. patentapplication Ser. No. 14/189,062 filed Feb. 25, 2014 for “METHOD ANDAPPARATUS FOR MAKING PREFORMED SEALS”, which is hereby incorporated byreference in its entirety.

BACKGROUND

The field of the disclosure relates generally to sealing surfacediscontinuities, and, more particularly, to seals for encapsulatinggaps, edges, ledges, and other discontinuities on an aircraft structure.

Many structures, such as aircraft structures, include a plurality ofassemblies that may create gaps, edges, ledges, and otherdiscontinuities where elements of the assemblies interface. Efficientand safe operation of an aircraft, for example, requires that suchdiscontinuities be sealed. Traditionally, such discontinuities aresealed by the direct application of wet sealant using a manuallyoperated extrusion device and hand tools. However, such directapplication of wet sealant poses several difficulties. Typically, otherwork must be delayed for 48 to 72 hours near the area of the structureto which wet sealant has been applied, to enable the wet sealant to curesufficiently to avoid contamination or damage impacts from other work.Moreover, in some circumstances, air may become entrained as the wetsealant is applied, or the manual application of wet sealant may involveshort pauses and restarts, each of which tends to create bubbles andvoids within the applied sealant. Furthermore, it may be necessary toapply successive layers, or “beads,” of wet sealant in a stacked fashionto achieve the desired thickness of the seal, and voids tend to occurbetween each layer.

In addition, the quality of application of the wet sealant may besensitive to temperature. Wet sealant material that is colder than anoptimal temperature tends to be too thick, and thus may not flowsufficiently to cover the discontinuity as intended. On the other hand,wet sealant material that is hotter than the optimal temperature maypartially cure during application, sometimes referred to as“cross-linking” of the wet sealant. Cross-linking in the wet sealantalso limits the ability of the sealant to flow smoothly to cover thediscontinuity as intended, and to be worked with hand tools into adesired configuration immediately after application. In each case,streams or strands of sealant may separate and re-enter the seal region,trapping air inside and/or failing to integrate fully with the seal.Often it may be difficult to precisely control the temperature of thewet sealant throughout an application.

Seal regions that have an undesirable number of bubbles and voids mustbe reworked, and typically the rework may be performed only after theoriginally applied sealant has cured for 48 to 72 hours, for the reasonsdescribed above. Furthermore, the reworked portions of the sealtypically must be allowed to cure for an additional 24 to 48 hours. Inaddition, pieces of re-entrant sealant may chip off during rework,creating a risk of foreign object debris for the rework.

Moreover, in some circumstances, an excess of wet sealant is applied toensure an acceptable performance of the seal. Such excess sealant canadd significant unnecessary weight to a structure such as an aircraft,adversely affecting the efficiency of operation. In addition, directapplication of wet sealant can create irregular outer edges of the sealthat are visually unappealing to customers. Thus, in some circumstances,direct application of wet sealant to structural discontinuities causesextended delays and increased expense in both manufacture and operation.The individuals who manually apply the wet sealant may need extendedtraining and years of experience in order to successfully avoid thedrawbacks described.

Some known seals use a cap or mold to control application of wet sealantdirectly to a structure, such as an aircraft. However, in at least somecases, the use of such a cap or mold does not prevent the entrainment ofair during application of the wet sealant. In addition, the use of a capor mold at the structure does not avoid the need to delay other work toenable the wet sealant to cure sufficiently to avoid contamination ordamage impacts.

Some known seals are molded or extruded into a desired shape prior toinstallation on a structure, such as an aircraft. However, at least someknown molding and extruding techniques also create defects in the seal.For example, during the injection of wet sealant into at least someknown molds, the viscous wet sealant flowing against the interiorsurfaces of the mold tends to stack up on itself, producing folds alongthe edges of the seal. In addition, during extrusion of wet sealantthrough at least some known extrusion dies, the viscous sealant materialtends to curl back toward the edges of the extrusion die, which deformsthe intended cross-sectional shape of the seal.

BRIEF DESCRIPTION

In one aspect, a method of making a preformed seal is provided. Themethod includes coupling a first section of a mold to a second sectionof the mold such that a mold cavity is defined. A cross-sectional shapeof the mold cavity corresponds to a cross-sectional shape of thepreformed seal. The method also includes providing a reservoir that hasa port in flow communication with a reservoir cavity. The reservoircavity extends to a parting surface of the reservoir. The method furtherincludes filling the reservoir cavity with wet sealant such that the wetsealant is flush with the parting surface, and a bead of wet sealantprotrudes from the port. Additionally, the method includes coupling thereservoir to the first section and the second section such that thereservoir cavity is in flow communication with the mold cavity at theparting surface, injecting wet sealant from a nozzle through thereservoir into the mold cavity, and curing the wet sealant in the moldcavity to make the preformed seal.

In another aspect, a mold for making a preformed seal is provided. Themold includes a first section, and a second section configured to beremovably coupled to the first section such that a mold cavity isdefined between the first section and the second section. Across-sectional shape of the mold cavity corresponds to across-sectional shape of the preformed seal. The mold also includes areservoir that has a port in flow communication with a reservoir cavity.The reservoir cavity extends to a parting surface of the reservoir. Thereservoir is configured to be removably coupled to the first section andthe second section such that the reservoir cavity is in flowcommunication with the mold cavity at the parting surface. When thefirst section, the second section, and the reservoir are coupledtogether, the mold is configured to enable wet sealant injected throughthe port to extrude from the reservoir cavity into the mold cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an example aircraft on whichembodiments of a preformed seal may be used;

FIG. 2 is a schematic diagram of an embodiment of a preformed sealapplied to an example structural discontinuity;

FIG. 3 is a schematic diagram of an embodiment of a mold configured formaking the preformed seal shown in FIG. 2;

FIG. 4 is a cross-sectional view of the mold shown in FIG. 3;

FIG. 5 is another cross-sectional view of the mold shown in FIG. 3;

FIG. 6 is a perspective view of a reservoir section of the mold shown inFIG. 3;

FIG. 7 is a perspective view of the mold shown in FIG. 3 prepared forsealant injection from a nozzle;

FIG. 8 is a perspective view of the mold shown in FIG. 3 during sealantinjection from a nozzle;

FIG. 9 is another perspective view of the mold shown in FIG. 3 duringsealant injection from a nozzle;

FIG. 10 is a schematic diagram of a molded length of the preformed sealshown in FIG. 2;

FIG. 11 is another schematic diagram of a molded length of the preformedseal shown in FIG. 2;

FIG. 12 is a schematic diagram of another embodiment of a preformed sealapplied to another example structural discontinuity;

FIG. 13 is a schematic diagram of the preformed seal shown in FIG. 12;

FIG. 14 is a cross-sectional view of an embodiment of a mold configuredfor making the preformed seal shown in FIGS. 12 and 13;

FIG. 15 is a schematic diagram of still another embodiment of apreformed seal applied to still another example structuraldiscontinuity;

FIG. 16 is a schematic diagram of the preformed seal shown in FIG. 15;

FIG. 17 is a cross-sectional view of an embodiment of a mold configuredfor making the preformed seal shown in FIGS. 15 and 16;

FIG. 18 is a schematic diagram of an embodiment of a nonlinear preformedseal;

FIG. 19 is a schematic diagram of another embodiment of a nonlinearpreformed seal; and

FIG. 20 is a flowchart of an embodiment of a method of making apreformed seal such as the preformed seals shown in FIGS. 2, 13, 16, 18,and 19.

DETAILED DESCRIPTION

The methods and apparatus described herein provide a preformed seal forgaps, edges, ledges, and other discontinuities in a surface of astructure, such as an aircraft. The methods and apparatus provide a sealwith a desired pre-determined cross-sectional shape, such as a shapethat fits a fillet defined on the surface of the structure. Thepreformed seal includes a reduced number of voids, bubbles, andre-entrant strands, which reduces or eliminates a need for rework afterthe seal is applied to the structure. In addition, other work on thestructure does not need to be delayed to allow the preformed seal tocure in place, and the preformed seal facilitates avoiding the use ofexcess sealant material.

Referring more particularly to the drawings, implementations of thedisclosure may be described in the context of a structure such as anaircraft 10 shown schematically in FIG. 1. Various components ofaircraft 10, such as, but not limited to, fuel tanks 12 and fuselage 14,contain discontinuities on structural surfaces, such as exemplarydiscontinuity 50 shown in FIG. 2. In the embodiment shown in FIG. 2,discontinuity 50 is a fillet formed at a joint between a firststructural member 52 and a second structural member 54. First structuralmember 52 and second structural member 54 may be, for example,overlapping panels of one of fuel tanks 12. A discontinuity surface 56is defined by an outer surface 60 of first structural member 52, an edgesurface 62 of second structural member 54, and an outer surface 64 ofsecond structural member 54. It should be understood that embodiments ofthe disclosure are not limited to the shape of discontinuity 50, and thecorresponding shape of preformed seal 100, illustrated in the exemplaryembodiment.

As illustrated schematically in FIG. 2, an exemplary preformed seal 100is applied to discontinuity 50. Preformed seal 100 includes a contactsurface 102 configured to be at least partially complementary todiscontinuity surface 56, facilitating a seal against fluid flow betweenfirst structural member 52 and second structural member 54 when seal 100is applied to discontinuity 50. In the embodiment shown in FIG. 2,contact surface 102 is defined by a first segment 110 configured to fitagainst outer surface 60 of first structural member 52, a second segment112 configured to fit against edge surface 62 of second structuralmember 54, and a third segment 114 configured to fit against outersurface 64 of second structural member 54. Preformed seal 100 alsoincludes a non-contact surface 104 and a cross-sectional shape 106defined between contact surface 102 and non-contact surface 104.

In the exemplary embodiment, cross-sectional shape 106 is selected tosatisfy at least one criterion with respect to seal 100. The at leastone criterion may be, for example, a minimum thickness for seal 100 atdiscontinuity 50. The minimum thickness may be defined based on, forexample, a minimum length of first segment 110, a minimum length ofthird segment 114, or any other suitable measure.

An exemplary mold 200 for making preformed seal 100 is illustratedschematically in a perspective view in FIG. 3. A cross-section ofexemplary mold 200 taken along line 4-4 is illustrated schematically inFIG. 4, and a cross-section of exemplary mold 200 taken along line 5-5is illustrated schematically in FIG. 5. With reference to FIGS. 3-5, inthe exemplary embodiment, mold 200 includes a first section 202, asecond section 204, and a reservoir 206. First section 202 and secondsection 204 each include a plurality of cooperating bolt holes 210 and212, respectively, one pair of which is illustrated by hidden lines inFIG. 3. Bolt holes 210 and 212 are configured to enable first section202 and second section 204 to be removably coupled together. Similarly,reservoir 206 includes bolt holes 214, and first section 202 and secondsection 204 each include at least one bolt hole 216 and 218,respectively, that cooperates with a corresponding bolt hole 214. Boltholes 214, 216, and 218 are configured to enable reservoir 206 to beremovably coupled to an interface end 234 of first section 202 andsecond section 204. In alternative embodiments, first section 202,second section 204, and/or reservoir 206 may be removably coupledtogether in any other suitable fashion.

First section 202 includes a first molding surface 220, and secondsection 204 includes a second molding surface 222. First molding surface220 is configured to be complementary to a first portion of the surfaceof preformed seal 100, and second molding surface 222 is configured tobe complementary to a second portion of the surface preformed seal 100.In particular, first molding surface 220 is complementary to non-contactsurface 104, and second molding surface 222 is complementary to contactsurface 102. When first section 202 and second section 204 are coupledtogether, a mold cavity 224 is defined between first molding surface 220and second molding surface 222 such that a cross-sectional shape of moldcavity 224 corresponds to cross-sectional shape 106 of preformed seal100. In the exemplary embodiment, mold cavity 224 extends throughinterface end 234 of first section 202 and second section 204, along alength 226 of first section 202 and second section 204, and through asecond end 228 opposite interface end 234. In alternative embodiments(not shown), mold cavity 224 terminates at a cap at second end 228 withan exhaust port defined therethrough.

Reservoir 206 includes a port 230 configured to allow wet sealantmaterial (not shown) to be injected therethrough. Port 230 is in flowcommunication with a reservoir cavity 232 defined in reservoir 206.Reservoir cavity 232 extends to a parting surface 236 of reservoir 206.When reservoir 206 is coupled to first section 202 and second section204, parting surface 236 is adjacent interface end 234 of first section202 and second section 204, such that reservoir cavity 232 is in flowcommunication with mold cavity 224.

In the exemplary embodiment, reservoir cavity 232 has a cross-sectionalsize and shape configured to facilitate a smooth extrusion of wetsealant material therefrom into mold cavity 224. For example, althoughmold cavity 224 includes portions 238 defined by surfaces that meet atacute angles, as illustrated in FIG. 4, reservoir cavity 232 does notinclude any pair of surfaces that meet at an acute angle, as illustratedin FIG. 5. As another example, a plurality of surfaces that definereservoir cavity 232 includes at least one pair of surfaces that meetsat an obtuse angle. Moreover, in the exemplary embodiment, across-sectional area of reservoir cavity 232 is substantially constantbetween port 230 and parting surface 236. Thus, reservoir cavity 232 isshaped to reduce a tendency of wet sealant material to stack up or curlin on itself, become trapped in narrow spaces, or curl outward whenapproaching, or exiting through, parting surface 236, while stillproviding a suitable area of flow communication with mold cavity 224. Inalternative embodiments, reservoir cavity 232 may have any suitableshape that allows the use of mold 200 to make preformed seal 100 asdescribed herein.

To make preformed seal 100 using mold 200, first molding surface 220 andsecond molding surface 222 are coated with a suitable release agent, andfirst section 202 and second section 204 are coupled together. Anexemplary release agent includes, but is not limited to, is a drylubricant such as a polytetrafluoroethylene-based release agent.Alternatively, when materials of the mold are sensitive to chemicalapplication, the release agent is a layer of polytetrafluoroethylenetape applied to the mold. The wet sealant 240 to be used (shown in FIG.6) is heated to a predetermined temperature. The predeterminedtemperature is in a range that facilitates smooth flow of wet sealant240, yet does not induce heat-related cross-linking of wet sealant 240.As discussed in the Background section, a smooth flow is one that flowssufficiently to cover discontinuity 50 as intended. Advantageously, mold200 may be used to make preformed seal 100 in a controlled environment,facilitating precise control of the temperature of wet sealant 240relative to a typical application of wet sealant 240 directly todiscontinuity 50. In certain embodiments, wet sealant 240 is PR-1776MB-2 sealant manufactured by PPG Aerospace, and the predeterminedtemperature is in a range from about 80 to about 90 degrees Fahrenheit.In an embodiment, the predetermined temperature is about 85 degreesFahrenheit.

As illustrated schematically in FIG. 6, reservoir 206 is positioned suchthat parting surface 236 faces upwards, and reservoir cavity 232 isfilled with wet sealant 240 such that wet sealant 240 is flush withparting surface 236 and a bead 242 of wet sealant 240 protrudes fromport 230. In the exemplary embodiment, filling reservoir cavity 232 withsealant 240 while reservoir 206 is uncoupled from first section 202 andsecond section 204 facilitates observation of, and prevention of,entrapment of air in wet sealant 240. Reservoir 206 is then coupled tofirst section 202 and second section 204. In alternative embodiments,reservoir is filled with wet sealant 240 after coupling to first section202 and second section 204.

As illustrated schematically in FIG. 7, after mold 200 is assembled andwet sealant bead 242 protrudes from port 230, mold cavity 224 is readyfor wet sealant injection. A nozzle 250 for injecting wet sealant 240 isprepared such that a bead 252 of wet sealant 240 protrudes from a tip254 of nozzle 250. As illustrated schematically in FIG. 8, nozzle tip254 is then inserted into port 230. Nozzle wet sealant bead 252 andreservoir wet sealant bead 242 cooperate to reduce or prevent entrapmentof air within wet sealant 240 as nozzle tip 254 is inserted into port230. After insertion of nozzle tip 254, nozzle 250 injects wet sealant240 into reservoir cavity 232. A collar 256 of wet sealant 240,initially formed by nozzle bead 252 contacting reservoir bead 242,surrounds nozzle tip 254 and continues to prevent entrapment of airduring the injection process.

In the exemplary embodiment, nozzle 250 injects wet sealant 240 at apressure above atmospheric pressure. In certain embodiments, nozzle 250injects wet sealant 240 at a pressure in a range of about 20 to about 40psig. In an embodiment, nozzle 250 injects wet sealant 240 at a pressureof about 30 psig. In alternative embodiments, a pressure lower than 20psig or higher than 40 psi is used to accommodate a viscosity of wetsealant 240, a surface characteristic of first molding surface 220 orsecond molding surface 222, and/or a material from which mold 200 isformed. The injection pressure causes wet sealant 240 to travel throughreservoir cavity 232 and extrude through parting surface 236 ofreservoir 206 into interface end 234 of mold cavity 224. Wet sealant 240traverses mold cavity 224 along length 226 and exits mold cavity 224 atsecond end 228, as illustrated schematically in FIG. 9, indicating thatmold cavity 224 is filled with wet sealant 240. When mold cavity 224 isfilled with wet sealant 240, injection stops, and mold 200 remainsassembled while wet sealant 240 cures. The portion of wet sealant 240cured within mold cavity 224 forms preformed seal 100.

After a suitable curing time, first section 202, second section 204, andreservoir 206 are uncoupled, and preformed seal 100 is removed. Incertain embodiments, the cure time is within a range of about 48 toabout 72 hours. Cured sealant material formed outside mold cavity 224 istrimmed from preformed seal 100, and preformed seal 100 is cleaned witha suitable solvent to remove any remaining release agent. Twoperspective schematic views of preformed seal 100 are shown in FIG. 10and FIG. 11. Preformed seal 100 formed in this manner has a moldedlength 116 substantially equal to length 226 of mold first section 202and second section 204.

In certain embodiments, at least one of first molding surface 220 andsecond molding surface 222 comprises a first portion 244 complementaryto non-contact surface 104 of preformed seal 100. Moreover, at least oneof first molding surface 220 and second molding surface 222 comprises asecond portion 246 complementary to contact surface 102 of preformedseal 100. For example, in the exemplary embodiment shown in FIG. 4,first portion 244 is coextensive with first molding surface 220, andsecond portion 246 is coextensive with second molding surface 222. Incertain embodiments, at least a portion of each of first portion 244 andsecond portion 246 is configured to impart desired properties tonon-contact surface 104 and contact surface 102, respectively.

In particular, first portion 244 has a smooth surface such thatnon-contact surface 104, formed adjacent to first portion 244 in mold200, has a relatively smooth finish that facilitates detection ofdefects in seal 100, is relatively less likely to trap foreign objectdebris, and offers a generally neat and pleasing appearance. In anembodiment, first portion 244 is configured such that non-contactsurface 104 has a surface roughness of about 63 RMS (“root meansquared”) or lower, as measured in accordance with ASME B46.1-2009. Incontrast, second portion 246 has a rougher surface such that contactsurface 102, formed adjacent to second portion 246 in mold 200, has arelatively rougher finish that facilitates better adhesive bonding ofseal 100 to structural surfaces in the region of discontinuity 50, suchas outer surface 60 of first structural member 52, edge surface 62 ofsecond structural member 54, and outer surface 64 of second structuralmember 54 (shown in FIG. 2). In an embodiment, second portion 246 isconfigured such that contact surface 102 has a surface roughness in arange of about 125 RMS to 250 RMS, as measured in accordance with ASMEB46.1-2009. In alternative embodiments, first molding surface 220 andsecond molding surface 222 each are configured to impart additional orother desired properties to non-contact surface 104 and contact surface102.

Another exemplary embodiment of a preformed seal, designated aspreformed seal 300, is illustrated schematically in FIG. 12 and FIG. 13.In the exemplary embodiment, a discontinuity 350 is located where afirst panel 352 perpendicularly abuts a second panel 354. For example,discontinuity 350 may be present in a stowage bin area in a passengercabin of aircraft 10 (shown in FIG. 1). Preformed seal 300 includes acontact surface 302 configured to be at least partially complementary toa discontinuity surface 356, facilitating a seal against fluid flowbetween first panel 352 and second panel 354 when seal 300 is applied todiscontinuity 350. In the embodiment shown in FIGS. 12 and 13, contactsurface 302 is defined by a first segment 310 configured to fit againstan outer surface 360 of first panel 352, a second segment 312 configuredto fit against an outer surface 362 of second panel 354, and a firstnotch segment 314 and a second notch segment 316 configured to fit intoa notch 364 defined between first panel 352 and second panel 354. In theexemplary embodiment, preformed seal 300 also includes a key segment 318disposed at the end of first notch segment 314 and second notch segment316. Key segment 318 is configured to facilitate locating seal 300properly and holding seal 300 in place.

Preformed seal 300 also includes a non-contact surface 304 and across-sectional shape 306 defined between contact surface 302 andnon-contact surface 304. In the exemplary embodiment, cross-sectionalshape 306 is selected to satisfy at least one criterion with respect toseal 300. The at least one criterion may be, for example, a minimumthickness for seal 300 at discontinuity 350. The minimum thickness maybe defined based on, for example, a minimum length of first segment 310,a minimum length of second segment 312, or any other suitable measure.

An exemplary mold 400 for making preformed seal 300 is similar to mold200 (shown in FIGS. 3-9). A cross-section of exemplary mold 400 isillustrated schematically in a perspective view in FIG. 14. Morespecifically, a first section 402 of mold 400 includes a first moldingsurface 420, and a second section 404 includes a second molding surface422. First molding surface 420 is configured to be complementary to afirst portion of the surface of preformed seal 300, and second moldingsurface 222 is configured to be complementary to a second portion of thesurface of preformed seal 300. In particular, first molding surface 420is complementary to first segment 310, second notch segment 316, and afirst portion of key segment 318 of contact surface 302, plusnon-contact surface 304. Second molding surface 422 is complementary tosecond segment 312, first notch segment 314, and a second portion of keysegment 318 of contact surface 302. When first section 402 and secondsection 404 are coupled together, a mold cavity 424 is defined betweenfirst molding surface 420 and second molding surface 422 such that across-sectional shape of mold cavity 424 corresponds to cross-sectionalshape 306 of preformed seal 300.

In certain embodiments, at least one of first molding surface 420 andsecond molding surface 422 comprises a first portion 444 complementaryto non-contact surface 304 of preformed seal 300. Moreover, at least oneof first molding surface 420 and second molding surface 422 comprises asecond portion 446 complementary to contact surface 302 of preformedseal 300. For example, in the exemplary embodiment shown in FIG. 14,first portion 444 includes the curved portion of first molding surface420, while second portion 446 includes the remainder of first moldingsurface 420 and all of second molding surface 422. In certainembodiments, at least a portion of each of first portion 244 and secondportion 246 is configured to impart desired properties to non-contactsurface 304 and contact surface 302, respectively. In particular, firstportion 444 and second portion 446 are configured to impart desiredsurface roughness characteristics to non-contact surface 304 and contactsurface 302, respectively, as described above with respect to mold 200and preformed seal 100. In alternative embodiments, first moldingsurface 420 and second molding surface 422 each are configured to impartadditional or other desired properties to non-contact surface 304 andcontact surface 302.

In the exemplary embodiment, other aspects of mold 400, such as areservoir and suitable structure for removably coupling first section402, second section 404, and the reservoir together, are essentially thesame as that described for mold 200. In addition, preformed seal 300 maybe made from wet sealant using mold 400 in essentially the same fashionas that described for making preformed seal 100 from wet sealant usingmold 200.

Yet another exemplary embodiment of a preformed seal, designated aspreformed seal 500, is illustrated schematically in FIG. 15 and FIG. 16.In the exemplary embodiment, a discontinuity 450 is located where asplice plate 458 is disposed between a first stringer 452 and a secondstringer 454. For example, discontinuity 450 may be present in a fuelcell located on a plurality of upper stringers of aircraft 10 (shown inFIG. 1). Preformed seal 500 includes a contact surface 502 configured tobe at least partially complementary to a discontinuity surface 456,facilitating a seal against fluid flow between first stringer 452 andsplice plate 458, and between splice plate 458 and second stringer 454,when seal 500 is applied to discontinuity 450. In the embodiment shownin FIGS. 15 and 16, contact surface 502 is defined by a first segment510 configured to fit against an outer surface 460 of first stringer452, a second segment 512 configured to fit against an outer surface 462of second stringer 454, a third segment 514 configured to fit against afirst outer side surface 464 of splice plate 458, a fourth segment 516configured to fit against an outer end surface 466 of splice plate 458,and a fifth segment 518 configured to fit against a second outer sidesurface 468 of splice plate 458. In the exemplary embodiment, contactsurface 502 also includes a first fillet 520 to facilitate installationover an edge defined by an intersection of first outer side surface 464and outer end surface 466, and a second fillet 522 to facilitateinstallation over an edge defined by an intersection of second outerside surface 468 and outer end surface 466.

Preformed seal 500 also includes a non-contact surface 504 and across-sectional shape 506 defined between contact surface 502 andnon-contact surface 504. In the exemplary embodiment, cross-sectionalshape 506 is selected to satisfy at least one criterion with respect toseal 500. The at least one criterion may be, for example, a minimumthickness for seal 500 at discontinuity 450.

An exemplary mold 600 for making preformed seal 500 is similar to mold200 (shown in FIGS. 3-9). A cross-section of exemplary mold 600 isillustrated schematically in a perspective view in FIG. 17. Morespecifically, a first section 602 of mold 600 includes a first moldingsurface 620, and a second section 604 includes a second molding surface622. First molding surface 620 is configured to be complementary to afirst portion of the surface of preformed seal 500, and second moldingsurface 622 is configured to be complementary to a second portion of thesurface preformed seal 500. In particular, first molding surface 620 iscomplementary to a first portion of non-contact surface 504. Secondmolding surface 622 is complementary to a second portion of non-contactsurface 504, first segment 510, second segment 512, third segment 514,fourth segment 516, fifth segment 518, first fillet 520, and secondfillet 522. When first section 602 and second section 604 are coupledtogether, a mold cavity 624 is defined between first molding surface 620and second molding surface 622 such that a cross-sectional shape of moldcavity 624 corresponds to cross-sectional shape 506 of preformed seal300.

In certain embodiments, at least one of first molding surface 620 andsecond molding surface 622 comprises a first portion 644 complementaryto non-contact surface 504 of preformed seal 500. Moreover, at least oneof first molding surface 620 and second molding surface 622 comprises asecond portion 646 complementary to contact surface 502 of preformedseal 500. For example, in the exemplary embodiment shown in FIG. 17,first portion 644 is coextensive with first molding surface 620, andsecond portion 646 is coextensive with second molding surface 622. Incertain embodiments, at least a portion of each of first portion 644 andsecond portion 646 is configured to impart desired properties tonon-contact surface 504 and contact surface 502, respectively. Inparticular, first portion 644 and second portion 646 are configured toimpart desired surface roughness characteristics to non-contact surface504 and contact surface 502, respectively, as described above withrespect to mold 200 and preformed seal 100. In alternative embodiments,first molding surface 620 and second molding surface 622 each areconfigured to impart additional or other desired properties tonon-contact surface 304 and contact surface 302.

In the exemplary embodiment, other aspects of mold 600, such as areservoir and suitable structure for removably coupling first section602, second section 604, and the reservoir together, are essentially thesame as that described for mold 200. In addition, preformed seal 500 maybe made from wet sealant using mold 600 in essentially the same fashionas that described for making preformed seal 100 from wet sealant usingmold 200. In certain embodiments, due to first fillet 520 and secondfillet 522 partially encapsulating complementary portions of secondmolding surface 622, cured preformed seal 500 must be flexed and/or slidlongitudinally to enable removal from second section 604 after mold 600is uncoupled.

Although preformed seals 100, 300, and 500 illustrate three potentialcross-sectional shapes for embodiments of preformed seals, it should beunderstood that in alternative embodiments, preformed seals may have anycross-sectional shape that is suitable for sealing a discontinuity ofinterest. In addition, alternative embodiments of preformed seals neednot be formed in linear pieces such as those illustrated in FIGS. 10 and11 for preformed seal 100. Suitable embodiments of a mold may be used tomake non-linear pieces of preformed seals of any desired cross-section,such as seals 700 and 702 illustrated in FIG. 18 and FIG. 19,respectively. Alternatively, smaller, substantially linear pieces ofpreformed seal may be spliced together as needed to cover non-lineardiscontinuities.

Embodiments of preformed seals, such as preformed seal 100, preformedseal 300, and preformed seal 500, may be applied to discontinuities,such as discontinuity 50, discontinuity 350, and discontinuity 450, inany suitable fashion. While examples will be discussed with reference topreformed seal 100 and discontinuity 50 as shown in FIG. 2, FIG. 10, andFIG. 11, it should be understood that the examples are instructive forother embodiments of preformed seals and discontinuities as well. Forexample, if discontinuity 50 has a length shorter than molded length 116of preformed seal 100, a piece of preformed seal 100 may be obtainedfrom storage and cut to measure. Alternatively, if discontinuity 50 hasa length longer than molded length 116 of preformed seal 100, multiplepieces of preformed seal 100 may be obtained from storage andbutt-spliced together during installation to seal discontinuity 50. Theconsistency in form and shape of preformed seal 100 provided by the useof mold 200 facilitates ease of splicing. Advantageously, pieces ofpreformed seal 100 may be stored for an essentially unlimited period oftime before use on discontinuity 50. In contrast, wet sealant typicallyhas a limited shelf life, such as 40 days, and where wet sealant is tobe applied directly to a structure such as aircraft 10, a portion ofunused wet sealant typically must be discarded.

In certain embodiments, an adhesive layer (not shown) is pre-applied tocontact surface 102 and covered with a protective removable backing (notshown) prior to using or storing preformed seal 100. Thus, certainembodiments permit the installation of preformed seal 100 using a simple“peel and stick” procedure. Additionally or alternatively, immediatelyprior to installation of preformed seal 100 on discontinuity 50, anadhesion promoter (not shown) may be applied to either or both ofcontact surface 102 and structural surfaces in the region ofdiscontinuity 50, such as outer surface 60 of first structural member52, edge surface 62 of second structural member 54, and outer surface 64of second structural member 54. Preformed seal 100 is then installed ondiscontinuity 50 and left in place while the adhesion promoter cures.

An exemplary method 800 of making a preformed seal, such as preformedseal 100, 300, 500, 700, or 702, using a mold such as mold 200, 400, or600, is illustrated in FIG. 20. Method 800 includes coupling 802 a firstsection of a mold, such as first section 202, 402, or 602, to a secondsection of the mold such as second section 204, 404, or 604, such that amold cavity, such as mold cavity 224, 424, or 624, is defined, wherein across-sectional shape of the mold cavity corresponds to across-sectional shape of the preformed seal. Method 800 also includesproviding 804 a reservoir, such as reservoir 206, comprising a port inflow communication with a reservoir cavity, wherein the reservoir cavityextends to a parting surface of the reservoir, such as parting surface236. Method 800 further includes filling 806 the reservoir cavity withwet sealant such that the wet sealant is flush with the parting surfaceand a bead of wet sealant protrudes from the port, such as port 230. Inaddition, method 800 includes coupling 808 the reservoir to the firstsection and the second section such that the reservoir cavity is in flowcommunication with the mold cavity at the parting surface, injecting 810wet sealant from a nozzle, such as nozzle 250, through the reservoirinto the mold cavity, and curing 812 the wet sealant in the mold cavityto make the preformed seal.

Each of the processes of method 800 may be performed or carried out by asystem integrator, a third party, and/or a customer. For the purposes ofthis description, a system integrator may include without limitation anynumber of aircraft manufacturers and major-system subcontractors; athird party may include without limitation any number of venders,subcontractors, and suppliers; and a customer may be an airline, leasingcompany, military entity, service organization, and so on. Moreover,although an aerospace example is shown, the principles of the disclosuremay be applied to other industries, such as the automotive industry.

Certain embodiments of a preformed seal, such as preformed seal 100,300, or 500, made according to embodiments of method 800 using a moldsuch as mold 200, 400, or 600, present properties that are superior toseals formed by application of wet sealant directly to a discontinuity.For example, excess sealant is applied in 50 to 70 percent of wetsealant applications directly to a structural discontinuity, andinsufficient sealant is applied in 15 to 20 percent of suchapplications. In addition, such applications produce seals with anaverage of 5 to 7 defects per foot of seal, and about 90 percent of suchapplications result in a visual appearance rated poor.

In contrast, the use of preformed seals made according to embodiments ofmethod 800 results in 0 percent excess or insufficient sealant, 0percent poor appearance, and an average of only 3 defects per 100 feet,or 0.03 defects per foot. As, such, preformed seals made according toembodiments of method 800 present properties that are unexpectedlysuperior relative to at least some known molded or extruded seals. Forexample, seals having the same cross-sectional shape and size asexemplary preformed seal 100, molded using prior art molds and processes(which tend to trap air within the mold cavity), typically have anywherefrom 1 to 50 defects per foot. Seals extruded using prior art extrusionprocesses typically cannot be made to have the same cross-sectionalshape and size as exemplary preformed seal 100, because the wet sealantwill not hold its extruded shape.

The embodiments described herein provide a method and apparatus formaking preformed seals that meet at least one criterion, such as aminimum thickness at a structural discontinuity to be sealed. Theembodiments provide preformed seals with fewer defects and an improvedappearance relative to the direct application of wet sealant to astructural discontinuity. Thus, the embodiments reduce or eliminate aneed for costly seal rework after installation on the structure.Moreover, the embodiments provide an enhanced ability to control surfaceproperties of the preformed seals, such as a surface roughness on acontact surface to facilitate improved adhesion to the structure. Theembodiments yield consistent and uniform seals that meet manufacturingcriteria without applying excess sealant, advantageously eliminatingunnecessary sealant weight from the structure, such as an aircraft. Inaddition, the embodiments enable seals to be formed and cured separatelyfrom a primary structural manufacturing process, reducing a totalrequired manufacturing time and facilitating enhanced environmentalcontrol over the seal forming process. Further, the embodiments includean extrusion from a reservoir into a mold that makes preformed sealswith unexpectedly superior properties relative to at least some knownmolded or extruded seals.

This written description uses examples to disclose variousimplementations, which include the best mode, to enable any personskilled in the art to practice those implementations, including makingand using any devices or systems and performing any incorporatedmethods. The patentable scope is defined by the claims, and may includeother examples that occur to those skilled in the art. Such otherexamples are intended to be within the scope of the claims if they havestructural elements that do not differ from the literal language of theclaims, or if they include equivalent structural elements withinsubstantial differences from the literal language of the claims.

1-11. (canceled)
 12. A mold for making a preformed seal, said moldcomprising: a first section; a second section configured to be removablycoupled to said first section such that a mold cavity is defined betweensaid first section and said second section, wherein a cross-sectionalshape of said mold cavity corresponds to a cross-sectional shape of thepreformed seal; and a reservoir comprising a port in flow communicationwith a reservoir cavity, wherein said reservoir cavity extends to aparting surface of said reservoir, said reservoir is configured to beremovably coupled to said first section and said second section suchthat said reservoir cavity is in flow communication with said moldcavity at said parting surface, wherein when said first section, saidsecond section, and said reservoir are coupled together, said mold isconfigured to enable wet sealant injected through said port to extrudefrom said reservoir cavity into said mold cavity.
 13. A mold inaccordance with claim 12, wherein said first section comprises a firstmolding surface that is complementary to a first portion of a surface ofthe preformed seal, and said second section comprises a second moldingsurface that is complementary to a second portion of the surface of thepreformed seal, said mold cavity is defined between said first moldingsurface and said second molding surface when said first section and saidsecond section are coupled together.
 14. A mold in accordance with claim13, wherein at least one of said first molding surface and said secondmolding surface comprises a first portion complementary to a non-contactsurface of the preformed seal, said first portion comprises a smoothsurface such that the non-contact surface of the preformed seal formedin said mold has a surface roughness of about 63 RMS or lower.
 15. Amold in accordance with claim 13, wherein at least one of said firstmolding surface and said second molding surface comprises a secondportion complementary to a contact surface of the preformed seal, saidsecond portion comprises a rough surface such that the contact surfaceof the preformed seal formed in said mold has a surface roughness in arange of about 125 RMS to about 250 RMS.
 16. A mold in accordance withclaim 12, wherein said reservoir cavity comprises at least one of across-sectional size and a cross-sectional shape configured tofacilitate a smooth extrusion of wet sealant therefrom into said moldcavity.
 17. A mold in accordance with claim 16, wherein said reservoircavity is defined by a plurality of surfaces, at least one pair ofsurfaces of the plurality of surfaces meets at an obtuse angle.
 18. Amold in accordance with claim 16, wherein a cross-sectional area of saidreservoir cavity is substantially constant between said port and saidparting surface.
 19. A mold in accordance with claim 12, wherein saidfirst section and said second section each comprise an interface end,said reservoir parting surface is adjacent to said interface end whensaid first section, said second section, and said reservoir are coupledtogether.
 20. A mold in accordance with claim 19, wherein said firstsection and said second section each comprise a second end opposite saidinterface end, said mold cavity extends through said interface end,along a length of said first section and said second section, andthrough said second end.
 21. A mold in accordance with claim 13, whereinsaid first molding surface and said second molding surface are coatedwith a release agent.
 22. A mold in accordance with claim 12, whereinsaid first section and said second section each comprise at least onecooperating bolt hole sized to receive a bolt therethrough for removablycoupling said first section and said second section together.
 23. A moldin accordance with claim 17, wherein no pair of surfaces of theplurality of surfaces meets at an acute angle.
 24. A preformed seal foruse in sealing a discontinuity defined between a first structural memberand a second structural member, said preformed seal comprising: anelongated body comprising: a non-contact surface; and a contact surfacecomprising a plurality of segments configured to fit against outersurfaces of the first structural member and the second structuralmember, said plurality of segments oriented to converge at thediscontinuity.
 25. The preformed seal in accordance with claim 24,wherein said plurality of segments are defined by planar surfacesextending along said elongated body.
 26. The preformed seal inaccordance with claim 24, wherein a fillet is defined between twosegments of said plurality of segments.
 27. The preformed seal inaccordance with claim 24, wherein said contact surface further comprisesa first notch segment and a second notch segment extending from saidplurality of segments, and a key segment extending from ends of saidfirst notch segment and said second notch segment.
 28. The preformedseal in accordance with claim 24, wherein said non-contact surface has anon-planar profile.
 29. The preformed seal in accordance with claim 24,wherein said non-contact surface has a surface roughness of about 63 RMSor lower.
 30. The preformed seal in accordance with claim 24, whereinsaid contact surface has a surface roughness in a range of about 125 RMSto about 250 RMS.
 31. The preformed seal in accordance with claim 24,wherein said non-contact surface and at least one segment of saidplurality of segments meets at an acute angle.